Breaking Oxygen Evolution Limits on Metal Chalcogenide Photocatalysts for Visible-Light-Driven Overall Water-Splitting

Metal chalcogenides are promising visible-light absorption materials; however, their application in overall water-splitting has long been hampered by the sluggish kinetics of oxygen evolution reaction (OER) and serious photocorrosion. Fundamentally, these critical issues are related to the behavior of photogenerated holes. Here, using ZnSe as a model catalyst, we achieve high-performance overall water-splitting in intrinsic activity and stability by facilitating the utilization of holes in the OER rather than self-corrosion. This is guided by our microkinetic analysis that the kinetic bottleneck of hole-mediated OER on ZnSe is the high reaction barrier and low concentration of holes reaching the photocatalyst surface. Accordingly, we radically modify the conduction characteristic of ZnSe surface layer into p-type to break the above OER bottleneck. The resulting ZnSe photocatalyst exhibits an impressive overall water-splitting performance in pure water with an ideal H2/O2 molar ratio of ∼2 and a solar-to-hydrogen conversion efficiency of 0.1891% without the assistance of any cocatalyst, outperforming ever-reported overall water-splitting of state-of-the-art metal chalcogenides under identical conditions. In addition, due to the greatly promoted OER, the critical photocorrosion issue is successfully suppressed on the engineered ZnSe photocatalyst. This work breaks the long-standing limitations of metal chalcogenides for overall water-splitting.